1. Field of the Invention
The present invention relates to a flow rate detecting apparatus having semiconductor chips suitably used for detecting, for example, an intake air flow rate of an engine.
2. Description of the Related Art
A Thomas meter or a heating wire flow meter using a platinum resistor wire has been known as a typical conventional flow meter. However, in such a conventional flow meter, the measuring element exposed to a fluid comprises a wire which is subject to disconnection due to vibration, mechanical impact or the like.
Another conventional flow meter is also known wherein a resistor film is deposited or printed on an insulating substrate such as a ceramic substrate. In this flow meter, since the measuring element is constituted by a film, it can withstand mechanical vibration or the like. However, since the resistor film is deposited or printed on the insulating substrate, it is difficult to perform micropatterning, and thus, the size of the measuring element is necessarily increased. As a result, the heat capacity of the measuring element is also increased, degrading the response characteristic of the flow meter.
In this conventional flow meter, there are provided an element for producing heat and detecting temperature by the produced heat and an element for detecting fluid temperature. The heat producing element includes a heater resistor mounted on a support member. Some heat is lost through the sppport member without being utilized as heat radiation, so that the sensitivity of the flow rate detection is deteriorated.